Dictionary of Audio Terminology - 0-9

0 dBu - Preferred informal abbreviation for the official dB (0.775 V); a voltage reference point equal to 0.775 Vrms.

0 dBV - Preferred informal abbreviation for the official dB (1.0 V); a voltage reference point equal to 1.0 Vrms.

0 dBm - Preferred informal abbreviation of the official dB (mW); a power reference point equal to 1 milliwatt. To convert into an equivalent voltage level, the impedance must be specified. For example, 0 dBm into 600 ohms gives an equivalent voltage level of 0.775 V, or 0 dBu (see above); however, 0 dBm into 50 ohms, for instance, yields an equivalent voltage of 0.224 V -- something quite different. Since modern audio engineering is concerned with voltage levels, as opposed to power levels of yore, the convention of using a reference level of 0 dBm is obsolete. The reference levels of +4 dBu, or -10 dBV are the preferred units.

0 dBr - An arbitrary reference level (r = re; or reference) that must be specified.

0 dBf - Preferred informal abbreviation of the official dB (fW); a power reference point equal to 1 femtowatt, i.e., 10-15 watts.

0 dB-SPL - The reference point for the threshold of hearing, equal to 20 microPA (micro Pascals rms). [Note: dB-SPL is defined differently for gases and everything else. Per ANSI S1.1-1994, for gases, the reference level is 20 microPA, but for sound in media other than gases, unless otherwise specified, the reference is 1 microPA.]

1/3-octave – (1) Term referring to frequencies spaced every one-third of an octave apart. One-third of an octave represents a frequency 1.26-times above a reference, or 0.794-times below the same reference. (2) Term used to express the bandwidth of equalizers and other filters that are 1/3-octave wide at their -3 dB (half-power) points. (3) Approximates the smallest region (bandwidth) humans reliably detect change.

1/f noise or Flicker Noise - Noise whose amplitude varies inversely with frequency. Mainly used in solid-state physics to describe noise with 1/f behavior, such as the noise resulting from impurities in the conducting channel, generation and recombination noise due to base current in transistors, etc.

1T DRAM - A one-transistor dynamic random access memory design that significantly reduces the area required for a single memory cell. This capacitor-less design works by storing a binary 1 as excess positive charge in the device body and a binary 0 as excess negative charge. First described by Pierre C. Fazan and Serguei Okhonin, Mikhail Naggoga and Jean-Michel Sallese in their paper, "A Simple 1-Transistor Capacitor-Less Memory Cell for High-Performance DRAMS."

3D Sound - A term used to describe a three-dimensional sound field. A true 3D sound field positions sound anywhere in a semi-spherical shell surrounding the listener. Sound must come from anywhere directly behind to directly overhead to directly in front of the listener and all points left and right. It if does not, it is not 3D sound.

3-dB down point or -3 dB point – In reference to a passband filter(s), the range of frequencies passed by an audio low-pass, high-pass or bandpass filter. Normally measured at the -3 dB point: the frequency point where the amplitude response is attenuated 3 dB (decibels) relative to the level of the main passband. For a bandpass filter two points are referenced: the upper and lower -3 dB points. The -3 dB point represents the frequency where the output power has been reduced by one-half.

3-to-1 rule – In reference to microphones - The rule for spacing multiple microphones, which says that the distance between them should be at least three times the distance from each microphone to its source. So, for example, if the microphones are placed one foot from their source then they should be spaced three feet apart. This reduces phase cancellations between adjacent microphones.

4-wire Kelvin connection - A 4-wire, 2-pair, connection used to make resistance measurements that are independent of the measuring lead resistance -- one pair is a current source and the other pair is a voltmeter.

5.1 - The digital audio multichannel format developed by the Moving Picture Experts Group for digital soundtrack encoding for film, laserdiscs, videotapes, DVD, and HDTV broadcast. The designation "5.1" (first proposed by Tom Holman of THX fame) refers to the five discrete, full bandwidth (20-20 kHz) channels -- left, right, & center fronts, plus left & right surrounds -- and the ".1" usually refers to the limited bandwidth (20-120 Hz) subwoofer channel, but can also refer to a special effects/feature channel.

6s or 6 Sigma - In 1986, Bill Smith, a senior engineer and scientist at Motorola, introduced the concept of Six Sigma (a registered trademark of Motorola, Inc.) to standardize the way defects are counted. It is a statistical methodology for improving quality control.

8-Track cartridge – In reference to recording - A popular, albeit short lifespan, analog tape format invented and patented by William Powell Lear, founder of Learjet, in 1963.

10Base-T – Ethernet speed up to 10 megabits/sec (Mbps).

100Base-T (also known as Fast Ethernet) – Ethernet speed up to 100 Mbps.

1000Base-T (also known as Gigabit Ethernet) – Ethernet speed up to 1 gigabit/sec, or 1000 Mbps.

10Gbase-T (also known as 10-Gbit Ethernet) - A version of Ethernet with a nominal data rate of 10 Gbit/s (billion bits per second), ten times faster than gigabit Ethernet.

1000Base-F - Uses fiber cable.

1000Base-CX - A standard for GE connectivity where the "C" means copper and "X" is a placeholder.

1000Base-SX ("S" for short wavelength laser) - For laser fiber cabling based on the Fiber Channel signaling specification for multimode fiber only.

1000Base-LX ("L" for long wavelength laser) - For laser fiber cabling also based on the Fiber Channel signaling specification for multimode or single-mode fiber.

1000Base-LH ("LH" for long haul) - A multivendor specification (each vendor has a set of transceivers covering different distances). While not an IEEE standard, the vendors are working to interoperate with IEEE 1000Base-LX equipment using the gigabit interface connector (GBIC) multivendor specification in order to provide a common form factor and greater flexibility.

10.2 - Somewhat tongue-in-check term created by Tom Holman (of THX fame) for his experimental surround system based on 5.1 surround sound, but with twelve channels.

12:00 Syndrome - The phenomenon affecting too many pro audio sound people whereby they feel obligated to set all rotary controls "straight up," or within an 11:00 to 1:00 aperture, thereby destroying all the product designer's good work to provide them with a large range of adjustment to cover contingencies.

16 2/3 rpm - Phonograph recording speed obtained using a half-speed converter on a 33 1/3 rpm machine, used for special recording purposes, but never a standard.

42V PowerNet - The official name for the 42 V automotive electrical power system. The value of 42 volts comes from a tripling of the normal 12 V car battery to 36 volts which measures 42 volts when running.

45 rpm record - The standardized phonograph recording speed selected for the single song record.

70-volt line constant-voltage - The standard specifies that all power amplifiers put out 70.7 volts at their rated power. So, whether it is a 100 watt, or 500 watt or 10 watt power amplifier, the maximum output voltage of each must be the same (constant) value of 70.7 volts.

94 dB-SPL - Equals 1 Pascal = one newton per square meter, which is the standard used to measure microphone sensitivity.

160 - Refers to the dbx 160 Compressor/Limiter designed by David Blackmer in 1976.

-174 dBm/Hz - The power in a one hertz bandwidth of a thermal noise source at the reference temperature of 290 kelvin (approximately room temperature). A noise floor rule-of-thumb.

232 – Short for RS-232. The standard serial interface (EIA/TIA-232-E)used on most personal computers. A format widely supported for bidirectional data transfer at low to moderate rates.

360 - The number of degrees in a circle.

414 - Refers to the AKG C-414 introduced in 1971, the first commercial solid-state condenser mic is still in production and still leads the pack.

451 - The number of degrees Fahrenheit that paper ignites. Made famous by Ray Bradbury's book, Fahrenheit 451.

485 – Short for RS-485. The standard describing the electrical characteristics of a balanced interface used as a bus for master/slave operation. Allows up to 32 users to bridge onto the line (as opposed to RS-422's need to daisy chain the interconnections). Same as EIA-485.

500 Series - An industry standard for a 3U card frame 19" rack first developed by Datatronix, then API Audio Products, Inc. in the late 1980s. A few years ago, the current company formed The VPR Alliance, which is the controlling organization.

550 - Refers to the API 550A Equalizer designed by Saul Walker in 1968.

670 - Refers to the Fairchild 670 Compressor Limiter designed by Rein Narma in 1959, while at Fairchild Recording Equipment Company in Long Island City, NY.

802.3af or PoE (Power over Ethernet) - The name for the technology defined by IEEE802.3af that allows Ethernet appliances to receive power as well as data over existing LAN CAT 5 cabling.

802.11 or IEEE 802.11 – A set of standards for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands.

1034 - Refers to the original Philips IC part number: TDA1034, which was made by Signetics after their acquisition by Philips, and renamed NE 5534 along with the more often seen dual version, NE 5532. Though not the first audio IC (that credit probably goes to the National Semiconductor LM 381) the TDA 1034/NE 5534 became the first choice for high-qualitity pro and consumer audio products. With a Slew Rate of 13 V/µs, a bandwidth of 10 MHz and a noise performance of 4 nV/√Hz, it set the standard for all audio ICs to follow.

1073 - Refers to the Neve 1073 Console Module designed by Rubert Neve in 1970.

1176 - Refers to the Universal Audio/UREI 1176 Peak Limiter designed by Bill Putnam in 1968. First use of FETs in audio acting as voltage variable resistors for gain control.

1394 – Refers to IEEE-1394 (aka Firewire) A joint Apple and TI implementation of the IEEE P1394 Serial Bus Standard. It is a high-speed (100/200/400 Mbits/sec now, with 1 Gbit/s on the horizon) serial bus for peripheral devices.

5532 - Refers to the original Signetics NE 5532. which is the dual version of the NE 5534, which is the renamed part number for the original Philips TDA 1034.

HistoryOfRecording.com acknowledges the Elsevier, Inc. publication, Audio Engineering know it all, the University of Washington Press publication, The Audio Dictionary, second edition, the Howard W. Sames & Co., Inc. publication, Audio cyclopedia, the Cambridge University Press publication, The Art of Electronics, Rane Corporation (Dennis A. Bohn, CTO), Houghton Mifflin Company publication, The American Heritage Dictionary of the English Language, Fourth Edition, the IEEE publication, IEEE 100: The Authoritative Dictionary of IEEE Standards Terms, Seventh Edition and Wikipedia in the preparation of this Dictionary of Audio Terminology.

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